1. Field of the Invention
The present invention relates to exposure apparatus, exposure methods, and device manufacturing methods, and more particularly to an exposure apparatus and an exposure method used in a lithography process to produce electronic devices such as a semiconductor device and a liquid crystal display device, and a device manufacturing method that uses the exposure apparatus and the exposure method.
2. Description of the Background Art
Conventionally, in a lithographic process to produce electronic devices (microdevices) such as a semiconductor or a liquid crystal display device, a projection exposure apparatus by a step-and-repeat method (the so-called stepper) that transfers a pattern formed on a mask (a reticle, a photomask or the like) onto a plate (a glass plate, a wafer or the like) on which a sensitive agent such as a resist is coated via a projection optical system, or a projection exposure apparatus by a step-and-scan method and the like is used.
Now, in recent years, a maskless type (without the use of a mask which is a fixed original plate) scanning projection exposure apparatus has been proposed that can form a device without using an expensive mask, regardless of the size (degree of fineness such as, for example, linewidth, pitch and the like) of the device pattern (for example, refer to Kokai (Japanese Patent Unexamined Application Publication) No. 2004-327660 bulletin). According to the scanning projection exposure apparatus described in Kokai (Japanese Patent Unexamined Application Publication) No. 2004-327660 bulletin, by changing a transfer pattern generated in a variable pattern generation device in synchronous with the substrate stage, a desired pattern can be generated easily. Furthermore, because the exposure apparatus does not have to be equipped with a mask stage, which is different from a conventional exposure apparatus using a mask, it becomes possible to reduce the cost and size of the exposure apparatus.
However, it has become clear recently that even when the exposure apparatus is the maskless type described above, or in other words, the variable forming mask (also called an active mask or an image generator) on which a variable pattern is formed is used, it is actually not easy to obtain a pattern image of a desired shape and size, needles to say in the case of a transmission type, but also in the case of a reflection type. The cause for this is considered to be the influence of various optical phenomena, such as for example, optical proximity effect (OPE) or the so-called flare, or aberration of the optical system on image formation of a pattern generated by the variable forming mask on a surface subject to exposure via an optical system, even in the case when the variable forming mask is used.